In my save I'm having issues with drones getting stuck near one of the depots.
Not behind trees or machines or pipes or anything. They finish mining, walk to the depot, drop off their ore, turn around and ... sort of ... freeze in place, then move a tiny bit, then freeze again, and then walk off.
Here's my save: https://gofile.io/?c=KqSjjY
When you load it, you're right by a depot, and there's actually a drone stuck on the depot, near the top right side. All the drones that get stuck on this depot get stuck there. Not all the drones get stuck, but soon after this one walks off, another gets stuck. Wait a bit more after that one walks off, and another will get stuck.
Not a big deal, perhaps, as the drones mine enough ore anyway.